1. Field of the Invention
This invention relates to a method for fabricating a seal-integrated separator comprising a separator body for a fuel cell and a seal integrally formed on the separator body.
2. Background Art
Some fuel cell units comprise: a membrane electrode assembly consisting of a solid polymer electrolyte membrane sandwiched between an anode gas diffusion electrode and a cathode gas diffusion electrode; and a pair of separators holding the membrane electrode assembly therebetween.
In a fuel cell of the above type, passages for a fuel gas, e.g., hydrogen, are formed on the anode side separator surface which faces the anode gas diffusion electrode, passages for an oxidizing gas, e.g., oxygen-containing air, are formed on the cathode side separator surface which faces the cathode gas diffusion electrode, and passages for a cooling medium are formed between two separators disposed adjacent to each other.
When the fuel gas is supplied to the reaction surface of the cathode gas diffusion electrode, hydrogen is ionized and moves to the cathode gas diffusion electrode through the solid polymer electrolyte membrane. The electrons generated during this process are sent to an exterior circuit, and used as DC energy. At the cathode gas diffusion electrode provided with the oxidizing gas, water is produced through the reaction of hydrogen ions, electrons, and oxygen. The surface of the separator opposite the diffusion electrode is cooled by means of the cooling medium flowing between the two separators.
Since each of the fuel gas, oxidizing gas, and cooling medium must separately flow through respective passages, seal means are required to separate each of the passages.
For example, seals must be provided: around communication ports which are formed, through a fuel cell stack, to distribute the fuel gas, oxidizing gas, and cooling medium to each fuel cell composing the fuel cell stack; along the outer periphery of the membrane electrode assembly; around the separator surface forming cooling medium passages; and along the outer periphery of both surfaces of the separator. The seal material is preferably selected from compliant materials having the appropriate resilience, such as organic rubber.